There exist enormous quantities of heavy hydrocarbons such as heavy petroleum crude oils and tar sand bitumen (the heavy hydrocarbons extracted from tar sands), as well as residual heavy hydrocarbon fractions obtained from heavy hydrocarbon crudes such as atmospheric tower bottoms products, vacuum tower bottoms products, crude oil residuum and heavy vacuum gas oils. These heavy crudes and residual hydrocarbon streams contain large amounts of organometallic compounds, especially those containing nickel and vanadium, organosulfur and organonitrogen compounds, and asphaltenes (high molecular weight polycyclic, heptane insoluble materials). In addition, these heavy crude and residual hydrocarbons are viscous and as such require a greater degree of processing to convert them into liquid materials that can be transported easily.
A number of alternate physical and chemical routes have been developed and are still being developed for converting heavy hydrocarbon materials into lighter liquid and gaseous fuels. Among the approaches available are physical separation processes such as vacuum distillation, steam distillation, and solvent deasphalting, various thermal conversion processes such as visbreaking, delayed coking, fluid coking and coke gasification, catalytic processes such as hydrotreating, hydrorefining and hydrocracking, as well as multistage catalytic and non-catalytic processes. Each of these approaches has one or more drawbacks. In physical separation processes such as vacuum distillation, steam distillation and solvent deasphalting, a liquid hydrocarbon fraction is recovered in low yield but the asphaltene and resinous materials are not converted into product and must be disposed of separately. The various thermal conversion processes such as visbreaking, delayed coking, fluid coking and coke gasification require high temperatures above 500° C. and generate a low quality by-product coke. In coke gasification, treatment of heavy hydrocarbons with steam and oxygen at high temperatures is necessary to produce a product gas, which must be utilized locally, and has a limited yield of lighter liquid hydrocarbon product.
There are various processes for treating heavy hydrocarbons with and without water with specific externally supplied catalyst systems, or in some cases a second reactant, and externally supplied hydrogen or hydrogen donors at specified temperatures above the critical temperature of water and at specified pressures, from below to above the critical pressure of water.
U.S. Pat. No. 4,067,799 (Breaden, Jr. et al.) discloses a catalytic process for production of low boiling hydrocarbon products by treating heavy hydrocarbonaceous oil with hydrogen gas in the presence of a catalyst comprising a metal (such as cobalt, nickel) phthalocyanine and a particulate iron component. However, the process of U.S. Pat. No. 4,067,799 uses no water and the metal content of the lower boiling hydrocarbon product is not reported.
U.S. Pat. No. 4,214,977 (Ranganathan et al.) discloses a process for hydrocracking of heavy oils such as oils extracted from tar sands by use of an aqueous iron-coal catalyst in the presence of excess hydrogen gas. However, while the process produces light oils from tar sand bitumen, the process operates in the absence of water (except residual water present from the preparation of the specific catalyst) requires coal in combination with an iron catalyst to reduce coke deposition and there is no mention of the metal content of the lower hydrocarbon product.
U.S. Pat. Nos. 4,298,460 and 4,325,812 (both by Fujimori et al.) disclose two and three zone processes for cracking sulfur-containing heavy oils into light oils and producing significant quantities of hydrogen and coke. U.S. Pat. No. 4,298,460 discloses a three zone process for reaction of sulfur-containing heavy oil with a reduced iron species to produce coke, hydrogen, hydrogen sulfide, desulfurized light oil of unspecified heavy metal content and the recycling of the iron-containing species in a two-step process. The reaction disclosed in U.S. Pat. No. 4,298,460 is not catalytic but requires at least 2.5 times (on a weight basis) as much iron-containing species as sulfur-containing oil; said reaction does not require the presence of water in the first zone but requires two separate zones to process the iron-containing species removed from the first zone and to produce significant quantities of hydrogen sulfide, hydrogen and coke. U.S. Pat. No. 4,325,812 discloses a two-zone process for cracking sulfur-containing heavy hydrocarbons into light oils and producing significant quantities of hydrogen. Like U.S. Pat. Nos. 4,298,460, 4,325,812 produces significant amounts of hydrogen and coke and is not really catalytic; at least equivalent amounts of sulfur-containing heavy oil and iron-containing species are contacted in the first zone. As in the case of U.S. Pat. No. 4,298,460, the metal content of the product produced in U.S. Pat. No. 4,325,821 is not specified.
U.S. Pat. No. 3,453,206 (Gatsis et al.) discloses a multistage hydrorefining of petroleum crude oil wherein the heavy hydrocarbon feedstock is treated in a first reaction zone with a mixture of hydrogen and water at a temperature above the critical temperature of water and at a pressure of at least 1000 pounds per square inch gauge (psig) and in the absence of a catalyst; the product from a first zone is a liquid which is further treated with hydrogen in a second reaction zone in the presence of a catalyst at hydrorefining conditions. However, this process requires a separate processing step to supply relatively large quantities of hydrogen from expensive starting materials such as naptha or other hydrocarbon feeds.
U.S. Pat. No. 3,501,396 (Gatsis et al.) discloses a process for desulfurizing and denitrifying oil which comprises mixing the oil with water at a temperature above the critical temperature of water up to about 427° C. (800° F.) and at a pressure in the range of from about 1000 to about 25000 psig and reacting the resulting mixture with externally supplied hydrogen in contact with a catalytic composite. The catalytic composite is characterized as a dual function catalyst which is acidic in nature and comprises a metallic component such as iridium, osmium, rhodium, ruthenium and mixtures thereof and an acidic carrier component having cracking activity.
U.S. Pat. No. 3,586,621 (Pitchford et al.) discloses a method for converting heavy hydrocarbon oils, residual hydrocarbon fractions, and solid carbonaceous materials to more useful gaseous and liquid products by contacting the material to be converted with a nickel spinel (nickel aluminate) catalyst promoted with a barium salt of an organic acid in the presence of steam.
U.S. Pat. No. 3,676,331 (Pitchford et al.) discloses a method for upgrading hydrocarbons and thereby producing materials of low molecular weight and of reduced sulfur content (but unspecified metal content) and carbon residue by introducing water and a catalyst system containing at least two components into the crude hydrocarbon fraction. Suitable materials for use as the first component of the catalyst system are the C8-C40 carboxylic acid salts of barium, calcium, strontium, and magnesium. Suitable materials for use as the second component of the catalyst system are the C8 -C40 carboxylic acid salts of nickel, cobalt and iron.
U.S. Pat. No. 3,733,259 (Wilson et al.) discloses a process for removing metals, asphaltenes, and sulfur from a heavy hydrocarbon oil. The process comprises dispersing the oil in water, maintaining this dispersion at a temperature between 399° C. and 454° C. (750° F. and 850° F.) and at a pressure between atmospheric and 100 psig, cooling the dispersion after at least one-half hour to form a stable water-asphaltene emulsion, separating the emulsion from the treated oil, adding hydrogen, and contacting the resulting treated oil with a hydrogenation catalyst in the presence of externally added hydrogen at a temperature between 260° C. and 482° C. (500° F. and 900° F.) and at a pressure between about 300 and 3000 psig.
U.S. Pat. No. 4,134,825 (Bearden et.al.) disclose a process for catalytic hydroconversion of heavy hydrocarbons oil charge stock having a Conradson carbon content of at least 5 weight percent. The process comprises charging the oil soluble metal compound in an amount ranging from 10 to about 950 weight ppm, calculated as the elemental metal, based on said oil chargestock, and converting the oil-soluble metal compound (preferably molybdenum compounds) to a solid non-colloidal catalyst within said oil in the presence of a hydrogen-containing gas by heating said oil to elevated temperature ranging from about 325-415° C. at a pressure ranging 500-5000 psig. The hydro conversion takes place at a temperature ranging from 440 to 468° C. at a pressure ranging from about 1000 to about 3000 psig. The effluent from the hydroconversion reactor is separated in a gas liquid separator where hydrogen and light hydrocarbons are removed overhead and the liquid stream containing the dispersed catalyst solid is either distilled, solvent precipitated or centrifuged to separate into a clean liquid product and concentrated slurry.
U.S. Pat. No. 8,128,810 (Bhattacharya et.al.) discloses a process for using catalyst with nanometer crystallites in slurry hydrocracking. The process comprises hydrocracking of hydrocarbon feed in presence of a catalyst comprising iron oxide and alumina at a temperature range of 400-500° C. under pressure in the range of 500 to 3500 psi, to produce lighter hydrocarbons. The iron sulphide crystallites have diameter in the nanometer range. The effluent is separated in a high-pressure separator into a gas and liquid component. The gaseous stream consists of about 35 to 80 vol % of the hydrocarbon product and is processed to recover hydrocarbons and hydrogen for recycle. The liquid stream is further separated into light vacuum gas oil stream, heavy vacuum gas oil stream and a pitch stream. At least a portion of the pitch stream is recycled back to the slurry reactor.
There is still a vast scope of working in the technology for upgrading the heavy hydrocarbon oils by hydrocracking. The coke formation during hydrocracking is a big limitation and there is a need to work out a process either to eliminate this or producing a high value coke to increase its commercial value.